1. Field of the Invention
The present invention relates to an antenna structure, and more particularly to an antenna structure that is able to be disposed on a dustproof slot cover of a portable electronic device.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Referring to FIGS. 1A and 1B, FIG. 1A is a perspective view of a conventional portable electronic device 1, and FIG. 1B is a sectional view taken along line A-A′ of FIG. 1A showing a relative position of an antenna 12 to a printed circuit board 13 of the portable electronic device 1. The portable electronic device 1 may be a mobile phone, a personal digital assistant (PDA) or a global positioning system (GPS) and includes a housing 11, an antenna 12, a printed circuit board 13, and a leaf spring 14. The antenna 12, the printed circuit board 13, and the leaf spring 14 are all disposed in the housing 11. The antenna 12 is welded to an inner top surface 15 of the housing 11. The printed circuit board 13 is arranged on an inner bottom surface 16 of the housing 11 and parallel to the antenna 12, so that a predetermined vertical distance d is maintained between the printed circuit board 13 and the antenna 12. The leaf spring 14 electrically connects the antenna 12 to the printed circuit board 13.
In the above-described conventional portable electronic device 1, the antenna 12 must be vertically spaced from the printed circuit board 13 by the distance d, which is referred to as a “clearance distance”, so as to avoid possible electromagnetic interference between the antenna 12 and the printed circuit board 13 that would lead to lowered signal reception and transmission efficiency of the antenna 12. Generally speaking, the predetermined distance d for the clearance distance is preferably more than 5 mm to effectively prevent the electromagnetic interference between the antenna 12 and the printed circuit board 13. As a result, the portable electronic device 1 has an increased volume due to the relatively large distance d for the clearance distance.
It is therefore a need to develop an improved antenna structure for portable electronic devices in an attempt to reduce the clearance distance required between the antenna and the printed circuit board without adversely affecting the signal reception and transmission efficiency of the antenna.